package main

import "fmt"

func main() {
	s := make([]int, 0)
	fmt.Println("len(s) =", len(s), "cap(s) =", cap(s)) // len(s) = 0 cap(s) = 0

	s = append(s, 1)
	s = append(s, 2)
	s = append(s, 3)
	fmt.Println("len(s) =", len(s), "cap(s) =", cap(s)) // len(s) = 3 cap(s) = 4
}
